The objectives of this proposal are to describe the surface ultrastructure of normal, junctional and malignant colonic and rectal mucosa. The dissecting microscope, light microscope and transmission electron microscope are used to complement the scanning electron microscope appearances and to obtain a deeper understanding of the morphology of the normal and abnormal colon. Information about the histogenesis of the structural changes induced by disease is being sought. Mucosal changes in individuals with chronic ulcerative colitis and the neoplasms arising in these patients are being studied. A preliminary investigation of experimentally induced colon carcinoma will also be initiated.